What is a characteristic of sequential phases in traffic signals?

Sequential phases in traffic signals are defined by their operation in a specific order, which ensures that traffic flows safely and predictably. The characteristic of these phases is that they cannot occur at the same time. Each phase is designed to control the traffic flow for different movements, such as left turns, through traffic, or pedestrian crossings, and they are timed in a way that allows for a clear transition from one phase to the next without overlap.

The traffic signal system is structured to avoid conflicts between different movements, which could otherwise lead to unsafe situations, such as vehicles proceeding in opposite directions simultaneously. By design, sequential phases ensure that one movement is completed before the next begins, thereby maintaining order and safety at intersections.

This concept distinguishes sequential phases from other possible configurations where multiple signals might be activated simultaneously, allowing for more complex traffic scenarios, such as in a protected left turn or concurrent pedestrian signals.